Studies have been focused on the serum IgG (IgG Smi), and particulary on the extent and location of the deletion of its H chain. Studies also continue on a patient with myeloma, hyperviscosity and amyloidosis associated with an IgG3 serum globin and excretion of lambda L chain fragments apparently deleted of much of the C lambda domain. Considerable progress has been made in determining the primary structures of IgG Gar. Studies continue on the isolation and identification of haptens bound to monoclonal Ig's of patients with myeloma, macroglobulinemia and other PCD's.